Efficient optical communication device

ABSTRACT

In one embodiment, an apparatus for optical communication is disclosed. An optical sub-assembly and optical platform may form the apparatus. Lasers contained in the hermetically sealed optical sub-assembly can be coupled to a modulator on the optical platform. The optical modulator can access an optical network using beams of light sent from the laser.

TECHNICAL FIELD

The present disclosure relates generally to methods and systems forcommunicating over an optical communication network.

BACKGROUND

Next generation optical solutions utilize silicon photonics in order toachieve power control and continued miniaturization. Using siliconphotonic optical modulators within transmitting optical sub-assemblies(TOSAs) for high speed data communication with greater than 40 gigabyte(Gb) transmission rates, one typically needs a continuous light sourcein the form of semiconductor lasers to be aligned to the modulatorsection where light is coupled from the laser to the modulator inputwith the help of individual lenses or lens arrays (to minimize alignmenteffort). Typically, the lens(es) and modulator are then hermeticallysealed inside a suitable enclosure to cool the components withoutforming condensation. While the creation of such optical devicesprovides increased throughput and miniaturized structures, the energyrequirements for these devices, however, remains high due to theelectrical energy required to cool the laser and other components (e.g.,modulator) hermetically sealed within the enclosure.

Accordingly, a solution is needed for an optical device with increasedenergy efficiency that also can retain high throughput characteristics.Additionally, a solution is needed for an efficient opticalcommunication device with high throughput that may be manufactured usinglower cost components.

BRIEF DESCRIPTION OF THE DRAWINGS

The components in the drawings are not necessarily to scale relative toeach other. Like reference numerals designate corresponding partsthroughout the several views.

FIG. 1 illustrates a perspective view of an optical communication deviceaccording to an implementation of the invention;

FIG. 2 illustrates a hermetically sealed laser sub-assembly showing asingle sub-mount with multiple lasers on it according to animplementation of the invention;

FIG. 3 illustrates a cross-section view of an optical communicationdevice according to an implementation of the invention;

FIG. 4 illustrates a perspective view of an optical communication deviceaccording to an implementation of the invention;

FIG. 5 illustrates placement of individual sub-mounted lasers on a TECaccording to an implementation of the invention;

FIG. 6A illustrates an individually sub-mounted laser according to animplementation of the invention;

FIG. 6B illustrates the placement of a single laser on a sub-mount on aTEC according to an implementation of the invention;

FIG. 6C illustrates the placement of two lasers on individual sub-mountson a TEC and illustrating routing of wire bonds including clearancecheck for wire bond capillary according to an implementation of theinvention;

FIG. 6D illustrates the placement of four lasers on individualsub-mounts on a TEC according to an implementation of the invention;

FIG. 6E illustrates the placement of four lenses and wire leads on fourindividually sub-mounted lasers on a TEC according to an implementationof the invention;

FIG. 7 illustrates a perspective view of the alignment of four lenses onfour lasers on individual sub-mounts on a TEC providing mechanicalstabilization and improved reliability according to an implementation ofthe invention;

FIG. 8A illustrates a perspective view of an optical communicationdevice with horizontal TEC mounting according to an implementation ofthe invention;

FIG. 8B illustrates a side view of the alignment of an opticalcommunication device according to an implementation of the invention;

FIG. 9A illustrates a perspective view of an optical communicationdevice according to an implementation of the invention;

FIG. 9B illustrates a side view of the alignment of an opticalcommunication device according to an implementation of the invention;

FIG. 10 illustrates a wafer configuration with pre-defined breaksaccording to an implementation of the manufacture of the invention;

FIG. 11 illustrates a silicon photonics chip (e.g., sub-mount) withpre-defined breaks according to an implementation of the manufacture ofthe invention;

FIG. 12A illustrates a silicon photonics chip and laser sub-mountmounted to a carrier wafer configuration with pre-defined breaksaccording to an implementation of the manufacture of the invention;

FIG. 12B illustrates the tooling of a wafer configuration withpre-defined breaks according to an implementation of the manufacture ofthe invention;

FIGS. 13A-E illustrate the tooling of an optical communication deviceaccording to an implementation of the manufacture of the invention;

FIGS. 14A-B illustrate the flow of signals in an optical communicationdevice according to an implementation of the invention;

FIGS. 15A-E illustrate the tooling of an optical communication deviceaccording to another implementation of the manufacture of the invention;

FIG. 16A illustrates a perspective view of an optical communicationdevice according to another implementation of the invention;

FIG. 16B illustrates a top view of an optical communication deviceaccording to another implementation of the invention;

FIG. 16C illustrates a cross-section view of an optical communicationdevice according to another implementation of the invention;

FIGS. 17A-B illustrate a silicon photonics chip and laser sub-mountmounted to a carrier wafer configuration with pre-defined breaksaccording to another implementation of the manufacture of the invention;

FIG. 18 illustrates a method of using an efficient optical communicationdevice according to one implementation of the invention; and

FIG. 19 illustrates a method of manufacturing an optical communicationdevice according to one implementation of the invention.

DESCRIPTION OF EXAMPLE EMBODIMENTS Overview

In accordance with an example implementation disclosed herein, anoptical communication device may comprise a laser within a hermeticallysealed sub-assembly for use in an optical communications network. Athermo-electrical cooler may also reside within the hermetically sealedsub-assembly for dissipating heat generated by the laser. A window mayform part of the hermetically sealed sub-assembly for communicating alight beam between the laser and an optical input situated outside thehermetically sealed sub-assembly. The optical input may be connected toan optical modulator outside the hermetically sealed sub-assembly tomodulate the light beam and send a modulated optical signal to anoptical communication network.

In another example implementation, a laser may receive at a hermeticallysealed optical sub-assembly an electrical input from an external source.In response, a laser on a sub-mount within the hermetically sealedoptical sub-assembly may be fired corresponding to the electrical input.An optical modulator outside of the hermetically sealed sub-assembly mayreceive the output of the first laser and modulate the light and sendthe modulated light to an optical communication network through anoptical connector that forms part of the optical communication device.

Description

In some optical network devices, lasers are used that requiretemperature control with a thermo-electrical cooler (TEC) to maintainoutput wavelength and/or power. To avoid condensation on temperaturecontrolled (cooled) areas, a hermetic enclosure is utilized to enclosethe electrical components, modulators, and lasers. For example, inoptical device applications, a transmitter optical sub-assembly (TOSA)may be created by hermetically sealing components inside a suitableenclosure. In this way the components (which typically include lasersand optical modulators) may be cooled without forming problematiccondensation within the optical device. Accordingly, the TOSA may takeelectrical input signals through connection leads and export the opticalsignals through an optical receptacle (e.g., an optical connector orpatch chord is inserted into a receptacle to guide light via fiber toits final destination) by way of the hermetically sealed laser andmodulator assembly enclosure.

While the creation of such an optical device provides increasedthroughput and miniaturized structures, the energy requirements forthese devices remains high due to the electrical energy required to coolthe laser and other components (e.g., modulator) hermetically sealedwithin the enclosure. This is in part at least because all of thecomponents are located on the TEC and multiple short wire bonds leadingto the modulator increase power consumption.

Further, because the modulator is within the hermetically enclosedstructure, the electrical leads including multiple RF lines must berouted through non-conducting insulation (e.g., ceramic) from the insideof the enclosure to the connector portion while maintaining thehermeticity of the package, thus creating additional manufacturingexpense and hardship. Additionally, the final design of the connectorremains high, as hermetic RF feed through is more costly compared to lowcost DC feed-through (e.g., glass or metal). Furthermore, manufacturingrequirements for perfecting height tolerances in the proper alignment ofthe lasers within the hermetically sealed enclosure remain strict, andin some cases manufacturing is prohibited or slowed due to theserequirements.

In an example implementation, the optical communication device disclosedherein may have a hermetic sub-assembly of lasers and thermo-electricalcoolers (TEC) integrated within a sturdy optical platform or bench whichfurther holds optical components—e.g., isolator, optical modulator,mirrors, connectors, and electrical chips/circuits. The cost of theinventive device may be reduced over conventional designs by usingTO-industry parts without compromising performance and guaranteeing thehighest yield possible. In various implementations disclosed herein,multiple lasers can be placed inside the hermetic package to allowmultiple channel transmissions. A window cap on the hermetic enclosuremay allow the unsealed components to receive and transmit informationfrom/to the hermetically sealed laser components. In this way, lessenergy is consumed by the device than conventional optical deviceconfigurations.

The present disclosure also provides methods for absorbing the largeheight tolerances of thermo-electrical coolers (TECs), which can be inthe range of plus or minus 0.1 millimeters (mm), without compromisingthe stability of the optical package. Additionally, exemplaryimplementations disclosed herein allow for the burn-in of individuallasers to maximize yield and still allow for an arrangement of lasers ona certain pitch to be able to use lens arrays and couple light to amodulator with multiple inputs on the same pitch. The laser may be on asub-mount, such as ceramic.

In further exemplary implementations disclosed herein, the inventiveoptical communication device may also have a window forming part of thehermetically sealed assembly for communicating between the laser and anoptical input situated outside the hermetically sealed assembly. Theoptical input and/or inputs may be coupled to an optical modulator(comprising silicon photonics) through which signal processing may beperformed on the signal from the laser. An isolator to direct the lasermay be either outside or within the hermetically sealed assembly. Theoptical communication device may also have an optical output forcommunication with an optical communications network. Various types ofoptical connectors for receiving an optical signal from the opticaloutput and accessing the optical communications network may also beused.

The TEC that may be used in the optical communication device can bevertically or horizontally oriented within the hermetically sealedassembly. If vertically oriented, height tolerance adjustments of thelaser may be made by adjusting the position of the laser vertically onthe TEC. If horizontally oriented, height adjustments between the laserand the optical input may be made by varying the bottom lid of thehermetically sealed assembly or the depth of the optical modulator ordepth of laser mounting. When the depth of the optical modulator orlaser is varied, a spacer below the modulator or within the hermeticallysealed enclosure below or above the TEC may be configured to account forheight adjustments.

Optionally, the optical communication device may have multiple lasers ona single sub-mount positioned on the TEC (instead of individual laserson a sub-mount) such that a spacer is positioned underneath thesub-mount and adjacent to the TEC to facilitate heat dissipationgenerated from the laser or lasers.

Exemplary implementations of the optical communication device describedin the present disclosure thus provide for a reliable, flexible, andsturdy optical communication device. One implementation may have atransmitting optical sub-assembly for which low cost components fromtransistor outline industry (high volume) may be used, such as astandard transistor outline header (TO-header), and window cap with lowcost glass/metal hermetic seal. Energy efficiency is provided byhermetically sealing limited areas, such as the cooled or un-cooledlaser(s) that may be used as continuous light sources. This allows forthe optical modulator and connector sections of the inventive opticalcommunication device to remain outside the hermetic package, providingadvantages as described herein. This also prevents costly hermetic radiofrequency (RF) feed through.

According to the various implementations, the disclosure provided hereinis capable of providing advantages over the conventional TOSA connector.First, the hermetic area disclosed herein may contain direct current(DC) lines and no radio frequency (RF) signals thus allowing cheaper andeasier routing than conventional designs. (This is in part becauseglass/metal feed-through with round pins is only effective for less than10-Gb speeds. Beyond 10-Gb speeds, ceramic multi-layer has superior RFperformance (less reflection/radiation and more transmission of RFsignals).) Specifically, preparing a feed-through of DC signals into thehermetic area is much cheaper and easier compared to routing RF signalsbecause simple glass/metal seals can be used versus multiple ceramiclayers mating with metal seals as required for RF routing. Second, theoptical communication device may comprise, in certain implementations,lower cost standard packaging parts, such as ceramic sub-mounts,standard window caps, and/or standard pin headers. Third, the opticalcommunication device may have a higher laser burn in yield due to thepreferred individual laser on a sub-mount design described herein whereindividual sub-mounts may be replaced instead of replacing a multiplelaser sub-mount due to a single laser failure. Fourth, the opticalcommunication device may produce lower power consumption because it onlyrequires that lasers within the hermetic package be cooled as opposed toelectronics contained within the modulator section as required byconventional devices. Fifth, the optical communication device mayproduce a lower passive head load since no short wire bonds from hot tocold are required. Sixth, the optical communication device provides anelegant solution for the separation of lasers and modulator by tiltingthe TEC 90-degress (or substantially vertical) to deal with TEC heighttolerances without compromising stability or requiring more complicateddesign features to absorb TEC height tolerances (like shimming, laser ormodulator height adjustment).

In one implementation disclosed herein, low-cost TO-header technologywith multiple I/O pins can be used to allow DC routing of laser biases,along with TEC current and temperature sensor connections (e.g.,connections for thermistor). The laser(s) can be mounted on individualsub-mounts (preferably low cost and high thermal conductivity ceramicsversus more costly silicon processed sub-mounts with lower thermalconductivity, which increases TEC power). This would allow individualburn in of each laser on sub-mounts and passing dies could be used forsubsequent assembly. That way burn in yield is maximized versussimultaneous burn in of several lasers on the same sub-mount which wouldmake the whole sub-assembly fail if only one laser burn-in failed.However, it is to be understood by those of ordinary skill in the art,that the sub-assembly could use any kind of sub-mounts covering bothindividual or group (wafer) burn in strategies.

If the preferred individual laser sub-mounts are implemented, the shapeof the sub-mounts may allow for each individual laser to be mounted onthe TEC top surface to allow light emission in line with the TO-packagecenter axis. This would also allow multiple sub-mounts with lasers to bearranged on a pitch of as little as 0.5 mm to match the pitch of thelens arrays and/or the modulator section pitch. To allow easy handlingand burn in of individual sub-mounts, it is preferred that they have aminimum size of 0.8 mm to 0.9 mm. Also, burn in requires minimum padsize on laser sub-mounts to make a reliable electrical contact (e.g.,with pogo pins). Optionally, the arrangement of several sub-mounts onthe TEC top surface can be alternating (or opposing) so that all oddchannels are facing one way and even channels are rotated the oppositeway (i.e., 180 degrees). This allows the sub-assembly to maintain thedesired smaller pitch (e.g., 0.5 mm). Otherwise, a pitch such as 1.0 mmwould be the minimum pitch size, accordingly limiting the packagingsize. In accordance with the individual sub-mount implementation, a cutout on one sub-mount side may be utilized to avoid interference with thelaser wire-bond of the adjacent channel. The clearance cut on thesub-mount can easily be added before sub-mount separation by a dicingblade without adding much cost. In contrast, conventional designs usemore costly reactive ion etching on silicon to create clearance cuts.

Electrical connection may be established by wire bonds from sub-mountpads to the TO-header pins (as discussed with reference to FIG. 6).Layout of both sub-mount and header pins can also be carefully chosen tomaintain a small footprint and still allow wire bondability. On thesub-mount backside where it makes contact with the TEC top surface,conductive epoxy can be used to electrically connect the sub-mount padto a metalized or patterned TEC top surface and/or additional patternedsubstrate mounted to the TEC top surface (i.e., could be a common groundfor all lasers). The electrical connection can be a 90-degree bend viathe conductive epoxy on the sub-mount pad close to back side to TEC topsurface. This would be the lowest cost solution (without a 90-degreeepoxy path, wire bonds would need to replace the connection becausethere is limited space/access for additional pads; wrapping metal padsaround edges opens up additional space to place pads but increases thecost for the sub-mount). Alternatively, as noted, sub-mounts withconductive paths wrapping around (multiple) edges could be used to havea wire-bond connection only. However, this would increase the cost ofthe sub-mounts.

Optionally, to increase the mechanical integrity of the laser sub-mountarray on a vertically mounted thermo-electrical top surface a framestructure can be glued to the front side of the sub-mounts connectingall sub-mounts with each other and increasing the stiffness of theassembly.

Each laser can be mounted at a controlled distance to the front face ofthe sub-mount. A first lens can then be aligned and glued to each of thefront faces of the sub-mounts to collimate or bend the laser light. Thisallows larger physical separation between the laser and the modulatorsection to accommodate the hermetic sealing with a window cap.Alternatively a lens array can be aligned and glued to the lasersub-mount front surfaces.

Accordingly, the hermetic sub-assembly comprised of a TO-header andwindow (lens cap) containing multiple lasers, TEC and temperature sensor(e.g., thermistor) builds a robust unit that can be easily handled andtested before being used in subsequent assembly steps. The opticalsub-assembly can then be aligned and fixed (by weld, glue and/or solder)within the optical bench so that the laser signal/light may behorizontal to the optical bench. This requires a 90 degree tilt of theheader with regards to the optical platform/bench. In this way, theoptical setup is immune against any TEC height tolerances. It alsoallows exact alignment of laser beams in x/y/z and angle to match theoptical height and position of the modulator such that the modulatorheight does not have to be strictly controlled. It should be noted thatthe use of a TEC is not mandatory for some implementations (e.g., CWDMor non-WDM). For those applications, the TO-header would only providehermetic package for the un-cooled laser(s), still allowing the usage oflaser(s) that requires hermetic packaging (which is required, forexample, by a majority of current commercially available Indiumphosphide lasers).

Consistent with this disclosure, the optical bench material may be avariety of materials, including but not limited to, kovar or CuW tomatch the silicon coefficient of thermal expansion (CTE) and to alsoprovide good heat sinking in case of CuW. Metal injection molding (MIM)can alternatively be used for the optical bench in order to reduce costfor higher volumes of the optical communication device. Typical metalinjection molding dimensional tolerances are acceptable for the presentinvention.

Alternatively, ceramic could also be used as optical bench material butit is more challenging to machine to the required shape. Additionally, ahybrid of ceramic/metal or metal/metal is an option if laser welding isrequired, especially for a connection between the TO-header and theoptical bench and the fiber optic connector/receptacle to the opticalbench.

According to one implementation of the manufacture of the inventiveoptical communication device, isolators between the lasers and modulatorwould be attached to the device, followed by the placement and adhesiveattachment of the modulator to the optical bench. Coarse alignment isalso acceptable in the event a secondary lens (or array) is used on themodulator input side (such a secondary lens alignment would require highprecision). Alternatively, a staggered layout of modulator inputchannels would allow larger secondary lenses and easier tooling access.Further, in another alternative implementation, all modulator inputs canbe on the same line and a secondary lens array could be used.

To route the modulator output light more easily to a fiber (array)connector, it is beneficial to have the modulator output side bedifferent than the input side to allow for an easier arrangement ofcomponents not available due to space constrains when arranging on thesame side. In any event, the fiber (array) connector placement andattachment to the optical platform/bench can be either the last orsecond-to-last optical alignment step depending on process preferencesfor manufacturing the optical communication device. As noted, individualor array lenses can be used.

As further disclosed herein, the optical bench can be designed such thatone or more driver integrated circuits can be mounted adjacent to themodulator or even placed directly on the modulator. Connection to aprinted circuit board (PCB) can be such that wire bonds or flexconnections used between an integrated circuit and PCB or alternativelya cut out on the optical bench could allow a ball grid array (BGA)attachment of the integrated circuits to the PCB.

A further aspect of an exemplary implementation of the opticalcommunication device disclosed herein includes the heat sinking of theTEC. In a vertical orientation, the heat has to take a 90 degree turnfrom header backside to the heat sink which is typically parallel to theoptical bench. By using high thermal conductivity steel for the headerand an appropriate heat sink, which makes contact to the header backside (e.g., copper finger), the temperature drop within the heat sinkpath can be minimized to an acceptable level (e.g., adding an additionalhigh thermal conductive material to the header backside offers the heata parallel path decreasing thermal resistance and temperature drop toambient temperature).

The figures disclosed herein provide further details for the inventiveoptical communication device.

FIG. 1 illustrates a perspective view of an optical communication device100 according to an implementation of the invention. The opticalcommunication device 100 may comprise two main components: the opticalplatform/bench 105 and the hermetically sealed optical sub-assembly 200.As shown, a modulator 110 (comprising silicon photonics) and a printedcircuit board (PCB) 115 may be fixably attached to the opticalcommunication device platform 105. Additionally, an electricalintegrated circuit 111 (e.g., a flip chip bonded via a BGA) may bebonded to the modulator 110.

One or more input lenses 120A-N may reside on the modulator 110 tocouple laser signals received from the optical sub-assembly 200 into thephotonic modulator 110 for processing. A laser output lens 125 on themodulator 110 may also be used to couple the output of the photonicmodulator 110 to an optical communication network through an opticalinterface 130 (such as the lensed fiber receptacle 130 shown in FIG. 1or alternative receptacles (not shown)). It should be noted thatadditional components may be placed on the optical bench/platform 105,including but not limited to passive electrical components and activedriver integrated circuits, main electrical PCB 115, and/or micro opticsturning mirrors. The electrical connection to the PCB 115 (or other mainelectrical board) can be done by a ball grid array (BGA) or can also bedone by flexible PCB or wire bond.

The optical interface 130 may comprise a variety of forms, including butnot limited to, a lensed fiber (shown in FIG. 1) or any other opticalreceptacle to allow a connection to an optical patch cord. Regardless ofthe type, the optical interface 130 can be attached to the opticalplatform (e.g., glued, soldered or welded) before or after the outputlens is aligned and put into place at the modulator output side tocouple maximum light into the optical interface 130.

FIG. 2 further illustrates the hermetically sealed optical sub-assembly200 according to one implementation of the invention. The sub-assembly200 provides an air-tight sealed enclosure for placement of a TEC 210and sub-mounted lasers 215A-N. As shown, to maximize heat dissipationand increase mechanical stability, a spacer 220 may be incorporatedunderneath the lasers 215A-N. This spacer 220 may comprise a material,such as ceramic, or other material intended to dissipate heat from thesub-mounted lasers 215A-N. The lasers 215A-N may be individuallysub-mounted (as discussed with regard to FIGS. 6A-E) or alternativelymounted together on a sub-mount. To direct the optical light or signalfrom the lasers 215A-N to the modulator 110, one or more lenses (or alens array) may be mounted adjacent to the lasers 215A-N. Metalized pads245 may be used to carry current to the sub-mounted lasers 215A-N. Asshown in FIG. 4, there may be a gap 310 between the TEC 210 and thelaser sub-mount (which is typically silicon) so that the electrical pads245 do not short on the TEC 210. If this gap is filled with electricalconductive adhesive (like silver filled epoxy), there is a risk ofelectrical shortage due to overflowing epoxy. Therefore, an epoxy thathas high thermal conductivity but is not electrically conductive ispreferred. For example, in one exemplary implementation, an epoxy filledwith ceramic particles can be used to provide a thermal, but notelectrical, conductive epoxy (as discussed further with regard to FIG.3).

The temperature inside the hermetically sealed sub-assembly 200 may bemeasured by a temperature sensor like thermistor 240. As further shownin FIG. 2, the optical sub-assembly may also comprise a window cap 230that allows laser light to reach the modulator 110 optical signal inputs120A-N (as shown in FIG. 1). In this implementation, an isolator 235 islocated next to the sub-mounted lasers 215A-N. However, as describedherein, this isolator 235 alternatively may be located outside thesub-assembly.

FIG. 3 illustrates a cross section view of an optical communicationdevice 100 according to an implementation of the invention. As shown inthis implementation, the TEC 210 and header 205 are turned 90-degrees toa substantially vertical position. Doing so allows for the heighttolerances to be easily accounted for between the location of themodulator 110 and the output of the lasers 215A-N. For example, thespacer 220, sub-mounted lasers 215A-N, and isolator 235 could beadjusted vertically to account for any variances arising between theplacement of the modulator 110 and the lasers 215A-N. Alternatively, thesub-assembly 200 itself could be adjusted when placed in the opticalplatform 105 to create proper alignment between the lasers 215A-N andmodulator 110, if required, before being fixably attached to the opticalplatform.

As also shown in FIG. 3, a gap 310 may be provided between the sub-mountof the laser (e.g., silicon) and the TEC 210 to prevent an electricalshortage at the laser. In this configuration, heat travels from thelaser (i.e., the source of the heat), down through the sub-mount, andthrough the spacer 220 to the TEC 210. Alternatively, as mentionedpreviously, the gap 310 may be filled with a high thermal conductivityepoxy (e.g., 3 W/mK), such as epoxy filled with ceramic particles, toimprove thermal performance, thus allowing the heat to travel directlythrough the epoxy to the TEC 210. An example illustrates the thermalefficiency gained through this approach. For example, with spacerthickness of t=0.5 mm, the laser temperature may be reduced byapproximately 1.2° C. and for t=2 mm, the reduction can be approximately0.5° C. (assuming the temperature of the laser is 50° C. and the ambienttemperature is 75° C.). This is significant, as with four lasers runningat 120 mA each, this amounts to a TEC power savings of 40 mW per 1° C.

FIG. 4 illustrates a perspective view of an optical communication deviceaccording to another implementation of the invention. As noted, theisolator 235 in this implementation is shown outside of the hermeticallyassembled sub-assembly 200. Further, this implementation illustratesthat the optical communication device 100 may connect to an opticalnetwork through any number of interface 130 configurations (e.g.,receptacles).

In the implementation shown in FIG. 5, individual sub-mounted lasers505A-N may be placed on a TEC in an opposing configuration toaccommodate a smaller pitch as previously discussed. This configurationmay be used as an alternative to the multiple lasers on a sub-mountconfiguration. In either case, to facilitate the exchange of laser lightor signals between the sub-assembly 200 and the modulator inputs 120A-N,the sub-mounted lasers beneficially have lenses 510A-N to focus orcollimate the laser light so that it may extend through the window cap230 and reach the modulator inputs 120A-N. Alternatively, a lens arraymay be used in place of individual lenses.

FIGS. 6A through 6E illustrate a preferred design and configuration forthe placement of individual sub-mounted lasers 505A-N according to animplementation of the invention. In FIG. 6A, a single sub-mounted laseris shown. The laser on individual sub-mount design comprises a laser 605with a wire bond, burn in pads 610 (for electrical contact during burnin needle or pin contact), and a clearance 615 cut to avoid contact withthe wire bond of adjacent lasers. As noted previously, the clearance 615may be formed by a dicing blade without adding much cost to themanufacturing process.

FIG. 6B further illustrates the placement of the single sub-mountedlaser 505 on the TEC 210 according to an implementation of theinvention. The laser on a sub-mount 505 may be glued or otherwisefixably attached to the TEC 210 and a wire bond may be extended to forman electrical connection to a pin on the header 205 or other pinassembly used in the hermetically sealed sub-assembly 200. In accordancewith FIG. 6C, a second sub-mounted laser 505 may be placed on the TEC210 adjacent to and opposing the first individually sub-mounted laser505. This configuration allows for efficient routing of wire bonds625A-N to pins on the header 205. Further, as shown, this placementallows adequate clearance for using a tool 620 to attach the wire bonds625A-N.

As shown in FIG. 6D, four sub-mounted lasers 505A-D have been placed onthe TEC 210 according to an implementation of the invention. Each may beconnected to respective pins 515A-N through wire bonds 625A-D. FIG. 6Eillustrates the placement of four lenses on the four lasers 505A-N onindividual sub-mounts on a TEC 210 according to a further implementationof the invention. As previously noted, a lens array could alternativelybe used in place of the individual lenses.

The positioning of the lasers 505A-N in a line in an opposing manner asshown in FIGS. 6B through 6E allows for a smaller controlled pitch.Preferably, this pitch can range from 0.5 mm to 1.0 mm, and a pitch of0.5 mm is shown in FIGS. 6D through 6E. This pitch provides advantagesbecause it allows for denser component arrangement, smaller footprintand lower cost.

In FIG. 7, an exemplary implementation of the sub-mounted laser 505A-Nconfiguration is shown with a metal (or other material) frame 705 thathas been optionally glued or otherwise fixably attached to thesub-mounted lasers 505A-N around the lenses 510A-N to stabilize thestructure. Such stabilization allows for more stable performance overall operations, conditions and in better reliability.

FIGS. 8A through 8B illustrate views of another optical communicationdevice according to an implementation of the invention. In FIG. 8A, theoptical communication device 100 comprises an optical bench/platform 805and a hermetically sealed optical sub-assembly 800 similar to that shownin FIG. 1. However, in FIG. 8A, the optical sub-assembly 800 designvaries. Specifically, as shown in greater detail in FIG. 8B, the TEC 210in sub-assembly 800 is positioned horizontal relative to the modulator110. Accordingly, sub-mounted lasers 215A-N (which may be mountedtogether or individually sub-mounted) are positioned on the top of theTEC 210 to provide heat dispersion required for the lasers. As notedpreviously, in some configurations the laser might not require a TEC 210within the hermetically sealed sub-assembly 800, in which case thelasers would be height adjusted with a spacer as required to meetalignment with the window cap 815 positioned between the lasers 215A-Nand the inputs 120A-N to the modulator 110. It is noted that even whenlasers do not require a TEC 210, they still require a hermeticallyenclosed space, thus use of the present invention is applicable toun-cooled lasers as well as cooled lasers.

As shown in FIG. 8B, when a TEC 210 is utilized, height adjustments ofthe TEC 210 in respect to 805 and/or the modulator 110 may be made byplacing the components using a tooling component (shown by dashed line840 in FIG. 8B) and then welding the bottom lid 825 with the TEC 210 atthe preferred height to metal ring 830 A-N. Additionally, FIGS. 8A-Billustrate that a second hermetic seal between 830A-N and 810 can beused to join the top metal lid 810 to the platform 805 (which, in thisimplementation, is multi-layer ceramic but may be any suitablematerial). Optionally, as shown in FIG. 8B, the modulator 110 andintegrated circuit board 115 may be pre-adjusted height-wise by the useof a spacer 820, which may be machined as a part of the platform 805 oradded afterwards during the manufacturing process. Also the brazed metalrings 830 A-N used in welding should comprise ceramic with inferior RFperformance. Therefore, the RF routing should go directly to the PCB asopposed to being routed via the ceramic. This may be done with wirebonds. While the isolator 235 is shown inside the hermetically sealedsub-assembly 800, it may alternatively be located outside the hermeticenclosure 800 as discussed previously (if required at all). Further, asillustrated in FIGS. 8A-B, the inventive optical communication device100 may be manufactured without the use of a standard TO-header,although it is economically preferable to use a TO header instead ofhermetic ceramic feed-through package.

The operation of the optical communication device 100 shown in FIGS. 8Aand 8B may be the same as that described previously. Specifically, acontinuous light may be fired from the lasers 215A-N. While firing, thelasers 215A-N are cooled by TEC 210. The laser light is passed throughlenses to collimate the light adjacent to the lasers and then focusedoutside the hermetically sealed optical sub-assembly 800, where they arecoupled to the optical modulator 110. As previously discussed, anisolator 235 may be situated inside or outside the hermetically sealedassembly 800. The modulator 110 then modulates the laser light based oninput from the PCB 115 and outputs the modulated signal to the opticalnetwork 130.

FIGS. 9A through 9B illustrate yet additional views of an opticalcommunication device 100 according to another implementation of theinvention. As shown in FIG. 9B, height tolerances may be adjusted in theoptical sub-assembly 900 by adjusting distance/height between 110 and820. With subsequent locking of 110 to 820 (e.g., via glue, welding, orsolder), the modulator 110 (silicon photonic chip) could be sitting onan additional carrier (not shown) which is adjusted in respect to 820.Especially for the locking method “welding,” this is preferred since thecarrier material could be weldable kovar metal. Further, as with theimplementation shown in FIGS. 8A-B, a spacer 820 may also be used toadjust other height adjustment on 110 side could be use of various shimsin stepped-height variations tolerances between the output of thesub-assembly 900 and the input(s) 120A-N to the modulator 110.(Similarly, height adjustments (instead of modulator height adjustments)could likewise be done inside hermetic area 810 between laser sub-mount215A-N and TEC 210 (not shown)). In either case as before, a window cap815 is employed to allow communication between the hermetically sealedlasers 815A-N and the modulator 110 (which in turn may send signals toan optical network through optical interface 130).

As discussed previously, the various implementations disclosed hereinoffer advantages over conventional designs. Such advantages includeincreased power performance (lower power consumption), more economicalpackaging designs, and potentially smaller device sizes. This list isnot exclusive, but includes other advantages recognized by those ofordinary skill in the art.

The present disclosure also provides an inventive method ofmanufacturing the inventive optical communication device 100. FIG. 10illustrates a subassembly consisting of carrier 1015, 1010 and 1005. Asingulated sub-assembly is shown, but it could be part of a wafer scaleassembly (i.e., a wafer of many carriers 1015). Carrier 1015 haspre-defined breaks 1020A-B according to an implementation of themanufacture of the invention. Such breaks 1020A-B ensure easy separationof modulator 1010 and laser section 1005 in subsequent process steps.Wafer scale assembly can have cost and handling advantages. Anadditional advantage is pairing up of specific laser sub-mounts andmodulators. The pairing can be kept throughout the whole processresulting in easier optical alignment process and better final opticalcoupling. For example, the modulator 1010 and laser sub-mount 1005 canbe aligned approximately adjacent to the breaks as shown. The completesubassembly 1000 can then be attached to the optical bench and headersimultaneously and separated afterwards using pre-defined break lines1020A-B. This manufacturing process allows sealing of the lasersub-mount portion without having the modulator in close proximity and inlimited tooling access (as shown in FIGS. 13B-E).

FIG. 11 illustrates a subassembly 1100 with pre-defined breaks 1115A-Baccording to another implementation of the manufacture of the invention.Similar to the implementation shown in FIG. 10, the breaks 1115A-B allowfor separation of laser portion 1105 and modulator portion 1110 insubsequent process steps. However, in this implementation, a largersingle silicon chip 1100 encompasses both portions, eliminating the needfor additional carrier 1015.

As shown in FIGS. 12A through 12B, if two separate sub-mounts are used(e.g., a laser sub-mount 1005 and a modulator 1010), a subassembly 1015with pre-defined breaks 1020A-B according to an implementation of themanufacture of the invention may be aligned using a tool 1205. In FIG.12A the two sub-mounts in a first, course align step are placedapproximately aligned with the pre-defined breaks 1020A-B. Proper heightalignment between the sub-mounts is guaranteed by bond line controlbetween 1015 and 1010 and between 1015 and 1005. However, to ensureproper side-to-side alignment, in one implementation a jaw tool 1205 maybe inserted into the space between the sub-mounts and opened as shown inFIG. 12B to position the two individual sub-mounts. (The jaw toolreferences off of the precision etched features on sub-mounts 1005 and1010). As shown, this may be performed after laser attach and burn infor 1005 but before the final placement of specific components such asthe isolator the modulator and laser lenses. However, such tooling couldbe performed at any time prior to final attachment of the sub-mounts.

Similarly, FIGS. 17A through 17B illustrate another method of aligningthe laser sub-mount section 1005 and modulator section 1010. As shown, afirst tool 1705A-B may be inserted into slots 1715A-B manufactured intothe sub-mount section 1005 and modulator section 1010, thus providingangular alignment. At the same time, a second tool 1710A-B may beinserted into inverted pyramids 1720A-B. The combination of the secondtool 1710A-B, which preferably comprises two elongated columns (e.g.,conical pins in a collet used to hold the component), each ending in apyramid or pointed shape, allows for proper lateral alignment whenplaced into the inverted pyramids 1720A-B. This is shown in detail inFIG. 17B, as second tool 1710A is pressed into the inverted pyramid slot1720A that is machined or chemically etched into the modulator section1010.

FIGS. 13A through 13E illustrate further tooling of an opticalcommunication device 100 according to an implementation of themanufacture of the invention. In FIG. 13A, a pre-formed tool 1305 holdsthe optical platform 105 in place against a header 205 (that isstationary during the tooling process). A second tool 1310 providesproper course alignment for placing the sub-mount or carrier wafer. InFIG. 13B, a subassembly 1100 with pre-formed breaks (as discussed abovewith reference to FIG. 11)—or alternatively a wafer 1015 pre-formed withbreaks (as discussed above with reference to FIG. 10)—is positioned ontop of the space next to the thermo-cooler 210 and on top of the opticalplatform 105. At this point epoxy may be used to secure the sub-mount1100 to the spacer 220 and optical platform 105. Curing can be performedin the fixture.

After cured, the portion of the subassembly 1100 between the breaks isbroken (i.e., cracked) under controlled conditions. This may beperformed by a controlled tooling split or controlled stress exposure toa weak area of the sub-mount. Whatever the case, the middle portion ofthe sub-mount 1100 (or wafer, if using a wafer configuration) can beremoved or will fall away, as shown in FIG. 13C. Next, as illustrated inFIG. 13D, the tooling members 1310, 1305 have been removed, along withthe optical platform 105, thus leaving the header 205 stabilized in thefixture with the TEC 210, laser sub-mount 1105, and spacer 220. Withthis increased access, a thermistor 1320 may be added for heatmonitoring and wire bonding may occur.

Following the completion of the wiring of the laser sub-mount 1105according to FIG. 13D, a hermetic sealing step (either projection weldor laser seam sealing) will secure the front cover 225 of the opticalsub-assembly 200 to the header 205. Tooling member 1305 and toolingmember 1315 may be used during this step. As previously described, theoptical sub-assembly comprises a window cap 230 for sending laserlight/signals. At this time, the enclosure of the sub-assembly 200 canbe hermetically sealed by soldering or welding around the joint betweenthe front cover 225 and the TO-header 205. After sealing 225 to 205,tooling 1305, 1310 and 1300 are joined together again. Notably,splitting and re-joining of 1305, 1310 and 1300 can be done repeatedlyand precisely if designed right such that optical coupling between 1005and 1010 is maintained without additional active re-alignment. Finallyoptical bench 105 and header 205 can be joined at interface 1350A and1350B to secure alignment permanently (attach methods could besoldering, laser welding or adhesive attach). The optical communicationdevice 100 can then be removed from the clasp and additional parts (suchas a PCB board and optical connector) can be added as required.

Optionally, one way of joining header 205 to optical bench 105 is torely on tooling maintaining the optical alignment between 1005 and 1010.This could be advantageous during manufacturing because it is faster andless expensive due to the avoidance of additional alignment steps.However, because optical coupling could be compromised, there could beapplications where this is acceptable, while other applications are lessforgiving and require highest possible coupling. In those cases, aftersealing of front cover 225 to header 205, an additional active multipleaccess alignment step could be required between header 205 and opticalbench 105 before both parts are joined at interface 1350A and 1350B.

In yet another implementation of the inventive optical communicationdevice 100 shown in FIGS. 14A-B, an input lens array 1410 could be usedin combination with an angled reflector 1405 to direct the opticalsignals into and out of the modulator 1005. The input array 1410 receivelasers light (here shown as receiving four laser beams as dashed lines)from the laser sub-mount. The modulator 1005 would then modulate thelight (by encoding data and multiplexing) the laser inputs and would inturn send a single light beam to the optical network. In FIG. 1, thelaser output lens (or lenses) 125 for the modulator 110 may be placedproximate to the optical connector 130. However, as shown in FIG. 14B,this may also be done by using an angled reflector that bends the light90 degrees and directs it to the optical interface/receptacle 130 thatinterfaces with the optical network. As such, various implementationsare envisioned for processing laser signals once coupled to themodulator 110, and the specific steps of processing performed by aphotonic modulator 110 are not mandated by this disclosure. As such, theinventive optical communication device 100 is not limited to anyspecific type or method of optical processing.

FIGS. 15A-E illustrate yet another tooling of an optical communicationdevice 100 according to an implementation of the manufacture of theinvention. In FIG. 15A, a pre-formed tool 1505 holds the opticalplatform 105 in place against a header 205 (that is stationary duringthe tooling process). A second tool 1515 provides proper coursealignment for placing the sub-mount or carrier wafer.

In FIG. 15B, a wafer 1000 with pre-formed breaks (as discussed abovewith reference to FIG. 10)—or alternatively a silicon chip withpre-formed breaks (as discussed above with reference to FIG. 11)—ispositioned on top of the space next to the thermo-cooler 210 and on topof the optical platform 105. As shown, the optical platform 105 has apre-formed area to insert a modulator 1000 for proper alignment. At thispoint epoxy may be used to secure the wafer 1100 (with sub-mountportions) to the TEC 210 and optical platform 105. Curing can beperformed in the fixture.

After cured, the portion of the wafer 1000 between the pre-formed breaksis cracked under controlled conditions. This may be performed by acontrolled tooling split or controlled stress exposure to a weak area ofthe sub-mount. Whatever the case, the middle portion of the wafer 1000(or chip, if using a silicon sub-mount configuration) can be removed orwill fall away, as shown in FIG. 15C. The tooling members 1510 and 1515are then removed, along with the optical platform 105, leaving theheader 205 stabilized in the fixture with the TEC 210 and lasersub-mount portion 1005. With this increased access, a thermistor may beadded for heat monitoring and wire bonding may occur.

Following the completion of the wiring of the laser sub-mount portion1005, a hermetic sealing step (either projection or weld or laser seamsealing) will secure the front cover 225 of the optical sub-assembly 200to the header 205 as shown to the right in FIG. 15C. Tooling member 1510and tooling member 1515 may then be re-inserted as shown in FIG. 15D.Notably, splitting and re-joining of tooling members 1505, 1510 and 1515can be done repeatedly and precisely if designed right such that opticalcoupling between sub-mount portions 1005 and 1010 is maintained withoutadditional active re-alignment.

As previously described, the optical sub-assembly comprises a window cap230 for sending laser light/signals. As shown in FIG. 15C, right side,the enclosure of the sub-assembly 200 can be hermetically sealed bysoldering or welding around the joint between the front cover 225 andthe TO-header 205. After sealing cover 225 to header 205, toolingmembers 1505 and 1510 and 1515 are joined together again. Finallyoptical bench 105 and header 205 can be joined at their interfaces tosecure alignment permanently (attach methods could be soldering, laserwelding or adhesive attach). The optical communication device 100 canthen be removed from the clasp and additional parts (such as a PCB boardand optical connector) can be added as required as shown in FIG. 15E.

As noted, the optical communication device 100 may comprise a number ofdifferent implementations. FIG. 16A illustrates yet another example ofthe optical communication device 100 according to another implementationof the invention. In this configuration, a window cap 230 is again usedto transmit laser light from inside the hermetically enclosedsub-assembly 200. As shown in FIG. 16A, a lid 1605 may be used to sealthe sub-mounted lasers after they are inserted in the cover 225 duringthe manufacturing process. Electrical leads 1625A-N (e.g., made from lowcost hermetic glass/metal seal) may be used to provide electrical inputto the lasers, which may be part of a laser-sub-mount, such as thesub-mount portion 1010 shown in FIG. 16B. A modulator portion 1005 maythen be positioned on an optical bench 105 outside of the sub-assembly200 to receive the laser light through the window cap 230. As describedpreviously, the modulator portion 1005 may then modulate signals usingthe light and utilize an interface (not shown) to access an opticalnetwork.

As shown in FIG. 16C, the TEC 210 is horizontal in this implementation,allowing height adjustments to be performed as previously noted withreference to FIGS. 8 through 9. However, in this specific exampleoptical bench 105 can be height adjusted by moving 105 up or down withreference to the optical sub-assembly 200 and, in particular, the windowcap 230, which are stationary. Once the right height is found, opticalbench/platform 105 can be permanently attached to the hermeticallysealed sub-assembly 200 and window cap 230 with laser welding asindicated with arrows in FIG. 16B.

Further, to achieve highest optical coupling, individual lasers 120A-Ncan be aligned, as a last step, to the modulator 110 rather than using alens array 1610 like the one shown in FIG. 16A. That way opticalmisalignment of the multiple collimated beams to each other can becompensated and maximum coupling can be achieved. However, ifapplications allow for less perfect alignment conditions, then the moreefficient lens array 1610 could be used instead.

Alternatively, to recover coupling loss in instances where, for example,optical coupling shifted too much following the window cap weld, anoptical flat (or window) may be used in the optical subassembly. Thismay be beneficial since the window in the window cap may not beperfectly aligned 90-degrees, but may have some random distribution inthe range of +/−2 degrees. Such a situation introduces beam walk(vertically to optical beam) in the range of 6 to 7 um. Accordingly,adding an optical flat and tilting it in an opposite way as the randomtilt of the window may be used to beneficially recover the coupling lossdue to beam walk. As such, a flat window of thickness “h” can beinserted into the collimated beam between the TO and waveguide and theflat window can be tilted and secured to shift the beam by distance “d”.In addition, a secondary recovery mode could be used to recover opticaltilt introduced by uncontrolled shift during the sub-assembly toplatform attachment. In this optional configuration, a single/doublewedge/prism could be used to recover loss and bend the collimated beamback to center (similar to that described with reference to the lensarray 1610).

In accordance with the above description, FIG. 18 illustrates an examplemethod 1800 of using an efficient optical device. At step 1805, ahermetically sealed optical sub-assembly receives an electrical input.This input may be generated from an outside source or a source residingat the sub-assembly. At step 1810, one or more lasers are fired withinthe hermetically sealed optical sub-assembly. As noted herein, thislaser or lasers may reside on a sub-mount and be affixed to athermo-cooler. At step 1815, the laser beam generated from the laser isthen received outside the hermetically sealed sub-assembly at amodulator. At this point, the modulator may or may not act on the beamto generate a signal for use in an optical communication network. Ineither case, however, at step 1820 the beam is directed through themodulator and output to an optical communication network. As noted, anynumber and type of optical connectors may provide access for the deviceto communicate with the optical network.

Further, in accordance with the above described manufacturing process,FIG. 19 provides an example method of manufacturing an opticalcommunication device according to one implementation of the invention.At step 1905, a laser sub-mount is positioned on a carrier waferadjacent to a first pre-defined break in a carrier wafer. (As notedpreviously, in another implementation not shown in method 1900,pre-defined breaks may be instead made in a single sub-mount that cancarry both a laser portion and a modulator portion in lieu of using acarrier wafer.) At step 1910, a modulator sub-mount is then positionedadjacent to a second pre-defined break in the carrier wafer.

In both instances, the sub-mounts may be glued or otherwise fixablyattached to the carrier wafer. Further, to ensure proper alignmentbefore or after adhesion material is applied, a jaw tool or invertedpyramid tool (as disclosed herein) may be used to align the twosub-mounts. After the modulator sub-mount is fixed, the laser-sub-mount(via the carrier wafer or in addition to the carrier wafer) may besecured to a thermo-electrical cooler at step 1915. Likewise, at step1920, the modulator sub-mount (via the carrier wafer or in addition tothe carrier wafer) may be secured to an optical platform to hold thesub-assembly and modulator components in place.

Once these sub-mounts are secured, the portion of the carrier waferbetween the two sub-mounts may be broken or cut away and removed at step1925. As discussed herein, the modulator section may optionally then beremoved to allow tooling access to the thermo-electrical cooler andlaser sub-mount. In any event, as noted at step 1930, the lasersub-mount and at least a portion of the thermo-electrical cooler issealed inside a hermetically sealed sub-assembly that contains a windowfor communicating between the laser sub-mount and modulator sub-mount.In particular, the window allows a laser beam to be fired from a laseron the hermetically sealed sub-mount and received by an input on themodulator that is not hermetically sealed. To achieve this, any of thealignment techniques disclosed herein may be used.

Although the subject matter herein has been described in languagespecific to structural features and/or methodological acts, it is to beunderstood that the subject matter defined in the appended claims is notnecessarily limited to the specific features or acts described above.Rather, the specific features and acts described above are disclosed asexample forms of implementing the claims.

What is claimed:
 1. An apparatus comprising: a hermetically sealedcomponent; a laser disposed within the hermetically sealed component; athermo-electrical cooler disposed within the hermetically sealedcomponent and configured to dissipate heat generated by the laser; and awindow forming part of the hermetically sealed component and configuredto permit transmission of a light beam between the laser and an opticalinput situated outside the hermetically sealed component.
 2. Theapparatus of claim 1, wherein the optical input is an input coupled toan optical modulator for performing signal processing on the light beamreceived from the laser.
 3. The apparatus of claim 2, wherein theoptical modulator further comprises at least one optical output forcommunication with an optical communications network.
 4. The apparatusof claim 3, further comprising an optical connector for receiving anoptical signal from the optical output and accessing the opticalcommunications network.
 5. The apparatus of claim 1, further comprisingan optical isolator located outside the hermetically sealed component.6. The apparatus of claim 1, further comprising an optical inputsituated outside the hermetically sealed component.
 7. The apparatus ofclaim 1, wherein the thermo-electrical cooler is vertically orientedwithin the hermetically sealed component relative to the apparatus toallow for height tolerance adjustments of the laser by adjusting theposition of the laser on the thermo-electrical cooler.
 8. The apparatusof claim 1, wherein multiple lasers on a sub-mount are positioned on thethermo-electrical cooler.
 9. The apparatus of claim 8, wherein a spaceris positioned underneath the sub-mount and adjacent to thethermo-electrical cooler to facilitate heat dissipation generated fromthe laser.
 10. The apparatus of claim 1, wherein a portion of thehermetically sealed component comprises a standard connector header forproviding a readily accessible electrical input for the laser.
 11. Theapparatus of claim 1, wherein the thermo-electrical cooler ishorizontally oriented relative to the apparatus within the hermeticallysealed component; and wherein height adjustments between the laser andthe optical input are made by varying at least one of the bottom lid ofthe hermetically sealed component or the depth of the optical modulator.12. The apparatus of claim 1, wherein a spacer is configured to accountfor height adjustments necessary to permit transmission of a light beambetween the laser and an optical input.
 13. A system comprising: anoptical platform configured to accept an optical modulator and ahermetically sealed sub-assembly; and a window forming part of thehermetically sealed sub-assembly for communicating a light beam betweena laser within the hermetically sealed sub-assembly and the opticalmodulator.
 14. The system of claim 13, wherein a thermo-electricalcooler is vertically oriented within the hermetically sealedsub-assembly to allow for height tolerance adjustments of the laser byadjusting the position of the laser on the thermo-electrical cooler. 15.A method comprising: receiving at a hermetically sealed opticalsub-assembly an electrical input; firing a first laser on a sub-mountwithin the hermetically sealed optical sub-assembly corresponding to theelectrical input; receiving outside the hermetically sealed opticalsub-assembly the output of the first laser on a sub-mount at an opticalmodulator; and sending an optical signal generated from the output ofthe first laser on a sub-mount to an optical communications networkthrough an optical connector.
 16. The method of claim 15, furthercomprising cooling the first laser on a sub-mount using athermo-electrical cooler that is vertically situated relative to theoptical modulator.
 17. The method of claim 15, further comprisingcooling the first laser on a sub-mount using a thermo-electrical coolerthat is horizontally situated relative to the optical modulator.
 18. Themethod of claim 15, further comprising configuring an isolator outsidethe sealed optical sub-assembly to isolate input from the first laser ona sub-mount.
 19. The method of claim 15, further comprising placing asecond laser on a sub-mount opposing the first laser on a sub-mountconfigured to allow space for wire bonding with a tool and such that thesignals of the lasers are aligned with a controlled pitch distance. 20.The method of claim 15, wherein a lens directs light from the firstlaser on a sub-mount to the optical modulator.